Having More Children Linked to Triple-Negative Disease

Research has shown that a woman's risk for hormone-receptor-positive breast cancer goes down as she has more children. A study reported in the Journal of the National Cancer Institute supports that link. But it also found that the more children a woman has, the higher her risk of triple-negative breast cancer.

Triple-negative breast cancer is:

estrogen-receptor-negative

progesterone-receptor-negative

HER2-negative

Overall, about 15% to 20% of breast cancers are triple-negative. Triple-negative cancers are usually more aggressive, harder to treat, and more likely to come back (recur) than cancers that are hormone-receptor-positive and/or HER2-positive. Hormonal therapy medicines and targeted therapy medicines such as Herceptin (chemical name: trastuzumab) and Tykerb (chemical name: lapatinib) usually don't work on triple-negative breast cancer.

This study analyzed information from the large, long-term Women's Health Initiative (WHI) study. The WHI wants to find any links between health, diet, and lifestyle factors and health problems such as cancer.

Of the more than 155,000 women in the WHI, 5,194 were diagnosed with invasive breast cancer about 8 years after joining the WHI. The researchers were able to clearly determine the hormone receptor and HER2 status of the cancer in 3,116 of the women who were diagnosed:

307 cancers were triple-negative

2,610 cancers were hormone-receptor-positive and HER2-negative

199 cancers were hormone-receptor-negative and HER2-positive

The researchers looked for any links between the number of children the women had and the risk of triple-negative breast cancer in these 3,116 women.

Women who had no children were 39% less likely to be diagnosed with triple-negative breast cancer but 35% more likely to be diagnosed with hormone-receptor positive breast cancer than women who had one or more children.

The more children a woman had, the larger her risk of being diagnosed with triple-negative breast cancer. Women who had three children were 46% more likely to be diagnosed with triple-negative breast cancer compared to women who only had one child.

The researchers aren't sure why having children increases triple-negative breast cancer risk. Still, understanding the factors linked to triple-negative breast cancer could help doctors understand why triple-negative breast cancer develops and how best to treat it.